Exemplary embodiments of the invention relate to a broadband signal junction with sum signal absorption (BSmS) for transmitting signals over a predefined bandwidth corresponding to the maximum bandwidth of a conventional T junction.
Such a broadband signal junction with sum signal absorption (BSmS) comprises a common hollow conductor with a first predefined cross-section and four side arm hollow conductors with a predefined second cross-section. Two first opposing side arm hollow conductors extend along a first axis. Two second opposing side arm hollow conductors extend along a second axis, wherein the first and second axes are disposed orthogonal to one another. The common plane runs orthogonal to a main axis of the common hollow conductor.
An orthomode coupler (orthomode transducer, OMT) is a passive component in microwave technology. It is used to split or combine orthogonally polarized electromagnetic waves. Current communications systems at this time consist of a satellite receiver and satellite transmitter with antennae for satellite supported communications. In such systems, the orthomode coupler assumes the function of a diplexer or circulator when received signals and transmitted signals are orthogonally polarized, and routes both signals together through an antenna.
Minor asymmetrical discontinuities can occur here due to manufacturing imprecision. This results in phase differences in the different electromagnetic waves, and ultimately leads to undesirable interference signals when the individual waves are combined. When the signals are combined, the relative phase shift in the individual propagation paths of the electromagnetic waves deviates slightly from a target value of 180°. If two signals are now subtracted from one another a substantial fraction of the sum remains, the amplitude of which depends on the deviation of the phase from the target value.
Such sum signals arise when conventional T junctions are used as a signal junction, as shown in FIG. 4, due to manufacturing tolerances. Because of the high quality of the orthomode coupler inside an antenna feed network, the sum signals resonate and cannot be absorbed for lack of a sum signal hollow conductor (port). This gives rise to undesired resonance peaks in the scatter parameters.
An advantage to the conventional T junction, as is shown in FIG. 4, is that it covers the maximum hollow conductor bandwidth of transmittable frequencies. If a signal is fed in at the so-called delta port of the symmetrical T junction, identified with 1, it splits to the two collinear side arms 2, 3 into −3 dB each of the output with a phase shift of ideally 180°, wherein the phase shift as described above can unfavorably deviate from 180° depending on manufacturing tolerances.
To dampen the resonance peaks, it is common to use a so-called magic T junction as a signal junction for coupling a signal instead of the conventional T junction. The sum signals that arise due to a relative phase shift are absorbed into the material of the hollow conductor absorber in this orthomode coupler.
In high-frequency technology, a hybrid or 3 dB coupler is called a magic T junction or hybrid tee. This component is used in microwave components in practice. It is a fixed power alternative to a rat race coupler used in microstrip line technology. The magic tee is a combination of an E-plane and an H-plane T junction. To guarantee correct functionality, a so-called matching structure is provided inside the magic T junction. The magic T junction only operates within a specific frequency range and the transmission behavior varies very significantly with the geometry of the matching structure.
The name magic T junction is derived from the electrical power flow inside the junction. An example of a magic T junction is shown in FIG. 5. A signal fed in at sum gate 8 splits to collinear side arms 6, 7 with identical amplitudes and phase positions.
In contrast, a signal fed in at difference gate 5 of the magic T junction splits to side arms 6, 7 with the same amplitude but a phase shift of 180°. The electrical field of the dominant field wave type in each gate is perpendicular to the broad side of the hollow conductor. This causes the signals 5S, 8S in the E-plane gate (difference gate 5) and in the H-plane gate (sum gate 8) to be polarized orthogonal to one another. As described, this variant is limited to about 40% of the bandwidth of conventional T junctions, which is a disadvantage.
Therefore, exemplary embodiments of the present invention are directed to a waveguide signal junction that suppresses undesirable resonance peaks in the scatter parameters at large bandwidths, in particular at a bandwidth corresponding to the bandwidth of a conventional T junction.
In accordance with exemplary embodiments of the present invention a waveguide signal junction for transmitting signals comprises a common hollow conductor with a first predefined cross-section and four side arm hollow conductors with a predefined cross-section. The cross-sections of the side arm hollow conductors can also vary. Two first opposing side arm hollow conductors of the four side arm hollow conductors extend along a first axis. Two second opposing side arm hollow conductors extend along a second axis. The first and second axes are disposed orthogonal to one another. In the broadband signal junction with sum signal absorption (BSmS) the two first side arm hollow conductors end at a hollow conductor absorber.
The broadband signal junction with sum signal absorption (BSmS) allows for the design of orthomode couplers that make it possible to increase the bandwidth and to significantly dampen the resonance peaks in the scatter parameters arising due to manufacturing tolerances. In particular, the broadband signal junction with sum signal absorption (BSmS) according to the invention is capable of being operated at a bandwidth corresponding to the bandwidth of a conventional T junction as is shown in FIG. 4, for example. The energy of the sum signals is decoupled to the side arm hollow conductors ending with the hollow conductor absorber and absorbed in the hollow conductor absorbers.
The first predefined cross-section of the common hollow conductor can be rectangular. The first predefined cross-section of the common hollow conductor can be square. The first predefined cross-section of the common hollow conductor can be elliptical. The first predefined cross-section of the common hollow conductor can be round. The first predefined cross-section of the common hollow conductor can basically have any arbitrary cross-section.
The second predefined cross-section of the four side arm hollow conductors can be rectangular. The second predefined cross-section of the four side arm hollow conductors can be square. The second predefined cross-section of the four side arm hollow conductors can be elliptical. The second predefined cross-section of the four side arm hollow conductors can be round. The second predefined cross-section of the four side arm hollow conductors can basically have any arbitrary cross-section.
According to another embodiment, the two second side arm hollow conductors can be disposed and/or designed in collinear fashion.
In another embodiment, the four side arm hollow conductors can be disposed or designed as displaced out of the common plane so that sets of two side arm hollow conductors are disposed in a common plane, respectively, for example, wherein the two planes are different planes. These two planes can be disposed parallel to one another or not parallel.
Furthermore, a matching structure can be provided inside the broadband signal junction with sum signal absorption (BSmS), in particular inside the common hollow conductor, the geometry of the structure being matched to a desired transmission behavior. For example, the matching structure is designed analogous to a magic T junction.
In another embodiment, the broadband signal junction with sum signal absorption (BSmS) according to the invention distributes or couples signals over an overall bandwidth with a phase shift of 180°.